Hemming apparatus for door belt part of vehicle

ABSTRACT

The present invention provides a pre-hemming apparatus for a door belt part for a vehicle. The apparatus includes a cam driver and a main punch pressing steel, and a cam device. The cam driver and the main punch pressing steel are installed at an upper die, and they are configured to drive the cam device installed at a lower die. The cam device installed at the lower die performs a hemming operation on a panel through a forward and backward motion and a linkage motion. The hemming apparatus performs the hemming operation including a first shifting process, a pre-hemming process, a second shifting process, and a main hemming process by allowing the cam driver and the main punch pressing steel to be linked with the cam device.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims under 35 U.S.C. §119 (a) the benefit of Korean Patent Application No. 10-2010-0124586 filed Dec. 8, 2010, the entire contents of which are incorporated herein by reference.

BACKGROUND

(a) Technical Field

The present invention relates to a hemming apparatus for a door belt part of a vehicle. More particularly, it relates to an apparatus that can perform hemming of a door belt part of a vehicle using a one-stroke process.

(b) Background Art

Generally, a door of a vehicle includes an inner panel and an outer panel that are combined by a hemming process.

The hemming process is a type of combination process for folding and joining the ends of the inner and outer panels, in which an end portion of the outer panel of the door is folded to surround an end portion of the inner panel.

When the hemming process is performed, an upper die and a lower die, manufactured according to the shape of each door, are installed at a hemming press, and then panels are positioned between the dies.

FIGS. 10A through 10D are schematic views illustrating a hemming process performed on a door belt part of a typical vehicle.

FIG. 10 A is a diagram illustrating a ready state of pre-hemming, in which a guide shaft (not shown) is introduced by a primary operation (i.e. the initial/beginning operation of the guide shaft by press). As shown, the panel 100 is provided with an end portion extending upwards (e.g. at about a 90° angle).

FIG. 10B is a diagram illustrating a completion state of pre-hemming. As shown, a 45° pre-hemming punch 110 performs a hemming process of providing the end portion of the panel 100 at an incline angle of about 45 degrees.

FIG. 10C is a diagram illustrating return of the pre-hemming punch 110 and initiation of main hemming, in which the 45° pre-hemming punch 110 returns by the operation of an air-cylinder 120.

FIG. 10 is a diagram illustrating a completion state of the main hemming, in which the end portion of the panel 100 is completely folded by a main hemming punch 130.

Thus, a typical hemming process adopts a mechanism that performs a two-stroke operation method wherein a door belt part is pressed twice to thereby hem the door belt part.

Accordingly, a typical hemming apparatus and method for a door belt part has limited productivity due to the two-stroke hemming operation, increased design time and hemming die manufacturing cost due to the complex hemming structure, increased labor for manufacturing the hemming die, and T/OUT (“Try Out”) and M/H (“Man Hour”) input increase at the vehicle body line.

Also, the typical hemming apparatus is further limited because it requires excessive assembly of various components, weighs 300 kg or more, has low line reparability, presents difficulty in replacement of consumable components due to upper die installation of cam, suffers from breakdown of the air cylinder, malfunction of the sensor and breakage of the hinge in the air cylinder, and has difficulty in main punch and pre-punch operations upon T/O due to upper die installation.

The above information disclosed in this Background section is only for enhancement of understanding of the background of the invention and therefore it may contain information that does not form the prior art that is already known in this country to a person of ordinary skill in the art.

SUMMARY OF THE DISCLOSURE

The present invention provides a hemming apparatus and method for a door belt part of a vehicle. The apparatus and method of the present invention implement a new type of hemming cam that performs a hemming operation of the door belt part with one-stroke, including a combination of a lower die installation structure of a cam and an upper die installation structure. The present invention, thus, provides improvement in productivity by use of a one-stroke process, reduction in manufacturing costs, and improvement of manufacturability by simplification of its structure.

In one aspect, the present invention provides a pre-hemming apparatus for a door belt part for a vehicle, including: a cam driver 10 and a main punch pressing steel 11 installed at an upper die for driving a cam device 12 of a lower die; and a cam device 12 installed at the lower die for performing a hemming operation on a panel through a forward and backward motion and a linkage motion. In accordance with this aspect, the pre-hemming apparatus performs the hemming operation, which includes a first shifting process, a pre-hemming process, a second shifting process, and a main hemming process, by allowing the cam driver and the main punch pressing steel to be linked with the cam device.

In a preferred embodiment, the cam device 12 may include a lower die base 13 fixedly installed at the lower die, a main body 14 supported slidably back and forth on the lower die base 13, a first link 17 including a shifting roller 15 and a pre-hemming roller 16 and installed in the main body 14 to have a rear-end pin structure and a second link 18 installed in the main body 14 to have a rear-pin structure and disposed parallel to and under the first link, a pre-hemming/main hemming punch 19 for performing a pre-hemming operation and a main hemming operation on the panel while moving in linkage with the first link 17 and the second link 18, and two return springs having one end fixed on the main body 14 and the other end fixed on pins of the first link 17 and the second link 18 to provide a restitution force to the first link 17 and the second link 18.

In another preferred embodiment, the lower die base 13 of the cam device 12 may include a guide rail 21 on one or both sides thereof to guide a forward and backward slide motion of the main body 14, a guide pin 22 penetrating the main body and for precisely guiding the forward and backward slide motion, and a return spring installed at the circumference of the guide pin 22 to provide a restitution force to the main body 14.

In still another preferred embodiment, the cam driver 10 may include a shifting bar 25 including a first pressing part 23 disposed at a lower portion of a front side thereof, a second pressing part 24 disposed at an upper portion of the front side thereof so as to protrude a greater degree than the first pressing part and vertically disposed in the center of the cam driver 10 and a pre-hemming bar 27 including a pre-hemming pressing part 16 disposed parallel to and at both sides of the shifting bar 25 and disposed vertical to the cam driver 10. The first pressing part 23 is configured for applying pressure for first shifting of the cam device 12, and the second pressing part 24 is configured for applying pressure for second shifting of the cam device 12. The pre-hemming pressing part 16 is configured for applying pressure for pre-hemming of the cam device 12 at a lower end portion of a front side thereof.

Other aspects and preferred embodiments of the invention are discussed infra.

It is understood that the term “vehicle” or “vehicular” or other similar term as used herein is inclusive of motor vehicles in general such as passenger automobiles including sports utility vehicles (SUV), buses, trucks, various commercial vehicles, watercraft including a variety of boats and ships, aircraft, and the like, and includes hybrid vehicles, electric vehicles, plug-in hybrid electric vehicles, hydrogen-powered vehicles and other alternative fuel vehicles (e.g. fuels derived from resources other than petroleum). As referred to herein, a hybrid vehicle is a vehicle that has two or more sources of power, for example both gasoline-powered and electric-powered vehicles.

The above and other features of the invention are discussed infra.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other features of the present invention will now be described in detail with reference to certain exemplary embodiments thereof illustrated the accompanying drawings which are given hereinbelow by way of illustration only, and thus are not limitative of the present invention, and wherein:

FIG. 1 is a perspective view illustrating a hemming apparatus for a door belt part of a vehicle according to an embodiment of the present invention;

FIG. 2 is a cross-sectional view illustrating a hemming apparatus for a door belt part of a vehicle according to an embodiment of the present invention;

FIGS. 3A and 3B are perspective views illustrating an upper die drive of a hemming apparatus for a door belt part of a vehicle according to an embodiment of the present invention;

FIG. 4 is a perspective view illustrating a lower die base of a hemming apparatus for a door belt part of a vehicle according to an embodiment of the present invention;

FIGS. 5A and 5B are perspective views illustrating a main body of a hemming apparatus for a door belt part of a vehicle according to an embodiment of the present invention;

FIG. 6 is a perspective view illustrating a first link and a second link of a hemming apparatus for a door belt part of a vehicle according to an embodiment of the present invention;

FIGS. 7A and 7B are perspective views illustrating pre-hemming/main hemming punches of a hemming apparatus for a door belt part of a vehicle according to an embodiment of the present invention;

FIG. 8 is a perspective view illustrating an installation state of a hemming apparatus for a door belt part of a vehicle according to an embodiment of the present invention;

FIGS. 9A through 9E are cross-sectional views illustrating an operation state of a hemming apparatus for a door belt part of a vehicle according to an embodiment of the present invention; and

FIGS. 10A through 10D are schematic views illustrating a hemming process performed on a door belt part of a typical vehicle.

Reference numerals set forth in the Drawings includes reference to the following elements as further discussed below:

10: cam driver 11: main punch pressing steel 12: cam device 13: lower die base 14: main body 15: shifting roller 16: pre-hemming roller 17: first link 18: second link 19: pre-hemming/main hemming punch 20a and 20b: return spring 21: guide rail 22: guide pin 23: first pressing part 24: second pressing part 25: shifting bar 26: pre-hemming pressing part 27: pre-hemming bar 28: pressing bar 29: pin bracket 30: main body stopper 31: pin plate 32a and 32b: pin hole 33a to 33f: pin 34a and 34b: link member 35: pin fitting part 36: punch part 37: contact portion 100: panel 140: upper die 150: lower die

It should be understood that the appended drawings are not necessarily to scale, presenting a somewhat simplified representation of various preferred features illustrative of the basic principles of the invention. The specific design features of the present invention as disclosed herein, including, for example, specific dimensions, orientations, locations, and shapes will be determined in part by the particular intended application and use environment.

In the figures, reference numbers refer to the same or equivalent parts of the present invention throughout the several figures of the drawing.

DETAILED DESCRIPTION

Hereinafter reference will now be made in detail to various embodiments of the present invention, examples of which are illustrated in the accompanying drawings and described below. While the invention will be described in conjunction with exemplary embodiments, it will be understood that present description is not intended to limit the invention to those exemplary embodiments. On the contrary, the invention is intended to cover not only the exemplary embodiments, but also various alternatives, modifications, equivalents and other embodiments, which may be included within the spirit and scope of the invention as defined by the appended claims.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings.

FIGS. 1 and 2 are a perspective view and a cross-sectional view illustrating a hemming apparatus for a door belt part of a vehicle according to an embodiment of the present invention.

Referring to FIGS. 1 and 2, the hemming apparatus for the door belt part of the vehicle may include a cam driver 10 and a main punch pressing steel 11 that are installed at an upper die thereof, and a cam device 12 that is installed at a lower die thereof.

The cam driver 10 may serve to provide a pressure for shifting (entering) operation and pre-hemming operation of the cam device 12. The main punch pressing steel 11 may be configured to provide a pressure for main hemming operation of the cam device 12. The cam device 12 may be configured to substantially perform a hemming operation on a panel in conjunction with the cam driver 10 and the main punch pressing steel 11.

Accordingly, the hemming operation may be performed by progressing through a first shifting process, a pre-hemming process, a second shifting process, and a main hemming process through a linked operation (traverse movement and linkage movement) of the cam device 12 as the cam driver 10 and the main punch pressing steel 11 move vertically.

The cam driver 10 may be fixedly installed at the upper die, such that vertical movement of the upper die causes the cam driver 10 to vertically move. The cam driver 10 moves vertically to contact and place pressure on the cam device 12, thereby moving the cam device 12.

As shown in FIGS. 3A and 3B, the cam driver 10 may include a central shifting bar 25 that is disposed perpendicular to the body of the cam driver 10, and pre-hemming bars 27 that are disposed parallel to and at both sides of the shifting bar 25.

Here, the shifting bar 25 may contact the first link 17 of the cam device 12 and the entire front and back (first entrance and second entrance) of the cam device 12. The pre-hemming bar 27 may contact a pre-hemming roller 16 of the first link 17 of the cam device 12 to rotate pre-hemming/main hemming punch 19 of the cam device 12.

For this, a first pressing part 23 may be formed at the front side of the shifting bar 25 and may be configured to apply pressure for first-shifting of the cam device 12, and a second pressing part 24 may be formed over the first pressing part 23 so as to protrude more than the first pressing part 23 and may be configured to apply pressure for second-shifting of the cam device 12. A pre-hemming pressing part 26 may be further provided so as to protrude from the lower end of the front side of the pre-hemming bar 27 and may be configured to apply pressure for pre-hemming of the cam device 12.

Accordingly, when the cam driver 10 descends, the pressing operation of the first pressing part 12 of the shifting bar 25, the pressing operation of the pre-hemming pressing part 26 of the pre-hemming bar 27, and the pressing operation of the second pressing part 24 of the shifting bar 25 may be sequentially performed such that the first entrance of the cam device 12, the rotation for the pre-hemming, and the second entrance of the cam device 12 are sequentially performed.

The main punch pressing steel 11, which is installed at the upper die to press the cam device 12, may descend together with the upper die and press the upper surface of the pre-hemming/main hemming punch 19 using three pressing portions thereof. Due to the pressing operation of the main punch pressing steel 11, the pre-hemming/main hemming punch 19 may be pressed down (in particular, rotated at a rotation radius of about R100, which is the radius of curvature of 100 nm) to perform main hemming on the panel.

The cam device 12 may include a lower die base 13 serving as a base, a main body 14 serving as a support, a pair of links including a first link 17 and a second link 18 that provide linkage movement, a pre-hemming/main hemming punch 19 for substantially performing the hemming, and two return springs 20 a restoring the pre-hemming/main hemming punch 19 to the initial position thereof.

As shown in FIG. 4, the lower die base 13, which is a member fixedly installed at the lower die, may serve to support the main body 14, and may also serve to guide forward/backward sliding movement of the main body 14.

To this end, guide rails 21 having a suitable configuration (e.g., an L-shape as shown) may be installed on one or both sides of the lower die base 13 to run parallel to each other. Two parallel guide pins 22 that are supported by a pin bracket 29 or the like may be horizontally installed at the front edge of the lower die base 13. In this case, return springs 20 b may be disposed around the guide pins 22.

A main body stopper 30 may be disposed at the rear edge of the lower die base 13 to protrude therefrom and to confine the main body 14 to a backward limit.

In this case, a thin plate, which is some embodiments is an oilless plate, may be disposed on the bottom of the guide rail 21 on which the main body slides 14. The plate may allow the main body 14 to slide back and forth more smoothly.

Here, a lower plate end portion of the main body 14 may be inserted into the guide rail 21 to guide the main body 14. The guide pin 22 may be penetrated by a pin plate 31 in the main body 14 to allow the main body 14 to move precisely in a straight line. The return spring 20 b may be flexibly supported between the pin bracket 29 and the pin plate 31 of the main body 14 to restore the main body 14 to its original position.

As shown in FIGS. 5A and 5B, the main body 14 may be a member that is supported slidably back and forth on the lower die, and may be a plate structure formed of a bottom plate and vertical walls at both sides thereof.

The vertical walls may have pin holes 32 a and 32 b in which pins 33 a, 33 b, 33 c and 33 d of the first link 17 and the second link 18 are fitted at upper and lower portions of the vertical walls, respectively.

Also, the vertical walls may have two pins 33 e and 33 f outwardly and horizontally extending at the upper end portions thereof. One end of the return springs 20 a and 20 b may be suspended by the pins 33 e and 33 f

The pin plate 31 having two holes may be vertically disposed on the bottom of the plate structure between the vertical walls of the main body 14. The holes of the pin plate 31 may receive the guide pins 22 over the lower die base 13.

As shown in FIG. 6, the first link 17 and the second link 18 may include a combination of two pairs of pins 33 a and 33 b, and 33 c and 33 d that are disposed in parallel so as to slide back and forth, with link members 34 and 34 b connected between the pins 33 a-33 d. Particularly, the front pin 33 a of the first link 17 may include the pre-hemming roller 16 for contacting the pre-hemming pressing part 26 in the cam driver 10, and the rear pin 33 b of the first link 17 may include a shifting roller 15 for contacting the first pressing part 23 and the second pressing part 24.

The first link 17 and the second link 18 may incline at a certain angle, and may be vertically disposed side by side. In this case, the first link 17 and the second link 18 may be supported by the rear pins 33 b and 33 d fitted into the pin holes 32 a and 32 b of the main body 14, and at the same time may be coupled to the pre-hemming/main hemming punch 19 through the front pins 33 a and 33 c.

Also, both end portions of the pin 33 a of the first link 17 and both end portions of the pin 33 c of the second link 18 may be connected to one end of the return spring 20 a extending from the main body 12. Accordingly, without requiring an external force, the first link 17 and the second link 18 may always return to their initial positions by the elastic force of the return spring 20 a.

The pre-hemming/main hemming punch 19 may be supported by a pin structure at the end of the first link 17 and the second link 18, and may perform pre-hemming and main hemming through linkage motion of the first link 17 and the second link 18.

To this end, as shown in FIGS. 7A and 7B, two pairs of pin fitting part 35 having holes for receiving pins may be disposed on the rear side of the body of the punch 19 formed of a rectangular plate. Also, a punch part 36 having a strip-like shape may be disposed on the front side of the body of the punch 19 to protrude therefrom and press the panel for hemming.

Three contact portions 37 corresponding to three pressing portions 28 of the main punch pressing steel 11 may be disposed on the upper surface of the punch part 36. The three contact portions 37 may be pressed by the main punch pressing steel 11.

Thus, the pin 33 a of the end of the first link 17 may be fitted into an upper portion of the pin fitting part 35 of the pre-hemming/main hemming punch 19, and the pin 33 c of the end of the second link 18 may be fitted into a lower portion of the pin fitting part 35 of the pre-hemming/main hemming punch 19. Accordingly, the pre-hemming/main hemming punch 19 may rotate in conjunction with the linkage motion (rotating about the rear pins) of the first and second links 17 and 18.

The return springs 20 a may provide a restitution force to the first and second links 17 and 18. Two return springs 20 a (total four) may be provided for each link. One end of the return spring 20 a may be fixed on the pins 33 e and 33 f of the main body 14, and the other end thereof may be fixed on each of pins 33 a and 33 c of the first and second links 17 and 18.

FIG. 8 is a perspective view illustrating an installation state of a hemming apparatus for a door belt part of a vehicle according to an embodiment of the present invention;

As shown in FIG. 8, an upper die 140 and a lower die 150 may be vertically disposed. A panel 100 may be positioned on the lower die 150.

A main punch pressing steel 11 and a cam driver 10 may be installed at the outer edge of the upper die 140, and a cam device 12 may be installed at vertical positions of the lower die 150, corresponding to the positions of the main punch pressing steel 11 and the cam driver 10.

Thus, when the upper die 140 operates, hemming may be performed on a panel 100 by a linkage motion between the main punch pressing steel 11 and the cam driver 10, and the cam device 12.

Accordingly, an operation state of a hemming apparatus for a door belt part of a vehicle will be described below.

FIGS. 9A through 9E are cross-sectional views illustrating an operation state of a hemming apparatus for a door belt part of a vehicle according to an embodiment of the present invention.

FIG. 9A illustrates a ready state of the cam driver 10, the main punch pressing steel 11, and the cam device 12 for hemming.

FIG. 9B illustrates a first shifting process.

As shown, when the panel is seated on a die, the cam device 12 may be drawn back to the rear side of the panel 100 at the initial operation state to provide interference with the panel 100. After the panel 100 is seated on the die, the cam device 12 may move forward to the upper die driver (e.g. by about 8 mm) to enter a pre-hemming standby state.

That is, since the cam driver 10 descends due to descent of the upper die, and the first pressing part 23 on the shifting bar 25 of the cam driver 10 contacts the shifting roller 15 of the first link 17 to apply forward pressure thereto, the entire main body 14 (including the pre-hemming/main hemming punch 19, the first link 17, and the second link 18) may move forward.

FIG. 9C illustrates a pre-hemming operation state.

After the first shifting is completed, pre-hemming may be performed by pressing the pre-hemming roller 16 using the pre-hemming driver to fold the panel 100 flange using the pre-hemming/main hemming punch 19 connected to the first link 17. The panel 100 flange may thus be folded at a suitable angle, such as about 43 degrees or 45 degrees with respect to the panel 100.

In particular, as the cam driver 10 further descends, and the pre-hemming pressing part 26 of the pre-hemming bar 27 contacts the pre-hemming roller 16 of the first link 17 to further apply forward pressure, the pre-hemming/main hemming punch 19 may move forward (particularly by rotating at a radius of about 100R) according to the rotation of the first and second links 17 and 18, and may allow the flange of the panel 100 to be folded at a suitable angle (e.g. about 45 degrees).

FIG. 9D illustrates a second shifting process.

After the pre-hemming, main hemming may be performed by moving the pre-hemming/main hemming punch 19 between the outer panel and the inner panel of the vehicle door, in which the cam device 12 may move forward (e.g. by about 17 mm) by the cam driver 10.

In particular, as the cam driver 10 further descends, and the second pressing part 24 of the shifting bar 25 contacts the shifting roller 15 of the first link 17 to apply forward pressure, the main body 14 (including the pre-hemming/main hemming punch 19, the first link 17, and the second link 18) may further move forward.

FIG. 9E illustrates a main hemming operation state.

After the pre-hemming/main hemming punch 19 moves between the outer panel and the inner panel of the vehicle door, the main punch pressing steel 11 may press the panels. In this case, since the pre-hemming/main hemming punch 19 is in a fixed state at this time, the punch 19 does not press the panel in a vertical direction, but rather may fold the flange while moving in an orbit or radius of about 100R. Here, the angle of the motion may vary according to the length of the flange.

In particular, as the main punch pressing steel 11 descends to press the upper portion of the pre-hemming/main hemming punch 19 in a state where the main body 14 (including the pre-hemming/main hemming punch 19, the first link 17, and the second link 18) moves forward, the flange of the panel can be folded.

Accordingly, the order of the hemming operations can be summarized as follows;

1) Cam operation initiation/first shifting starting point

2) Complete first shifting

3) Roller touch and pre-hemming operation staring point

4) Complete pre-hemming operation

5) Initiate return of pre-hemming/main hemming (occurs in an interval between pressing of pre-hemming pressing part and pressing of second pressing part)

6) Second shifting starting point

7) Complete second shifting and wait main hemming.

8) Main hemming starting point

9) Complete main hemming and complete cam operation.

The present invention advantageously improves productivity, reduces the manufacturing cost for a hemming die, and facilitates the fabrication of the hemming die, by providing a cam device that enables one-stroke hemming for a door belt part.

A hemming apparatus for a door belt part of a vehicle according to an embodiment of the present invention can improve the productivity and reduce the manufacturing cost according to a hemming die design through simplification of its components and structure, and can improve manufacturability through simplification of fabrication of a hemming die by adopting a one-stroke system that is configured with a combination of a cam driver installed at an upper die and a cam device installed at a lower die. Also, the hemming apparatus of the present invention is reduced in weight, has improved of line reparability, has improved T/O due to lower die installation, requires less labor for manufacturing a die, and provides quality T/O convenience due to ease of cam timing control.

The invention has been described in detail with reference to preferred embodiments thereof. However, it will be appreciated by those skilled in the art that changes may be made in these embodiments without departing from the principles and spirit of the invention, the scope of which is defined in the appended claims and their equivalents. 

1. A hemming apparatus for a door belt part for a vehicle, comprising: a cam driver and a main punch pressing steel disposed at an upper die; and a cam device disposed at a lower die; wherein the cam driver and main punch pressing steel are configured for driving the cam device, wherein the cam device is configured for performing a hemming operation on a vehicle panel through a forward and backward motion and a linkage motion, wherein the hemming apparatus performs the hemming operation through a first shifting process, a pre-hemming process, a second shifting process, and a main hemming process by allowing the cam driver and the main punch pressing steel to be linked with the cam device.
 2. The hemming apparatus of claim 1, wherein the cam device comprises: a lower die base fixedly disposed at the lower die; a main body supported slidably back and forth on the lower die base; a first link comprising a shifting roller and a pre-hemming roller, the first link installed in the main body to have a rear-pin structure, and a second link installed in the main body to have the rear-pin structure, the second link disposed in parallel under the first link, a pre-hemming/main hemming punch configured for performing a pre-hemming operation and a main hemming operation on the vehicle panel while moving in linkage with the first link and the second link; and a plurality of return springs having a first end fixed on the main body and a second end fixed on pins of the first link and the second link to provide a restitution force to the first link and the second link.
 3. The hemming apparatus of claim 2, further comprising: a guide rail disposed on opposing sides of the lower die base configured to guide a forward and backward slide motion of the main body; a guide pin penetrating the main body and configured for guiding the forward and backward slide motion of the main body; and a return spring disposed at the circumference of the guide pin and configured to provide a restitution force to the main body.
 4. The hemming apparatus of claim 1, wherein the cam driver comprises a shifting bar comprising: a first pressing part disposed at a lower portion of a front side of the shifting bar, and configured for applying pressure for first shifting of the cam device 12, a second pressing part disposed at an upper portion of the front side of the shifting bar, the second pressing part protruding from the shifting bar more than the first pressing part and being vertically disposed at a center of the cam device, the second pressing part configured for applying pressure for second shifting of the cam device; and a pre-hemming bar at a lower end portion of the front side of the shifting bar and being disposed at both sides of and parallel to the shifting bar, and vertical to the cam driver, the pre-hemming bar comprising a pre-hemming pressing part for applying pressure for pre-hemming of the cam device.
 5. A method for hemming a door belt part for a vehicle comprising: using the hemming apparatus of claim 1 to hem a door belt part by using a one-stroke process wherein the first shifting process, the pre-hemming process, the second shifting process, and the main hemming process are all performed in the one-stroke process. 